The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometric size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering the associated costs. Such scaling down has also increased the complexity of IC processing and manufacturing.
For example, there is a growing need to perform higher-resolution lithography processes. One lithography technique is extreme ultraviolet lithography (EUVL). The EUVL technique employs scanners that use light in the extreme ultraviolet (EUV) region, having a wavelength of about 1-10 nm. Some EUV scanners provide 4 times reduction projection printing, similar to some optical scanners, except that the EUV scanners use reflective optics rather than refractive optics, i.e., mirrors instead of lenses.
EUV radiation is absorbed in virtually all transmissive materials, including gases and glasses. To minimize unwanted absorption and to avoid EUV intensity loss, EUV lithography patterning is maintained in a vacuum environment. Each lithography step may employ a reticle through which the pattern of a component of an integrated circuit is generated. The reticle stage used in EUV scanners typically uses electrostatic attraction instead of vacuum suction to secure reticles.
Although existing methods and devices for transporting reticles in EUV scanners during the lithography process have been adequate for their intended purposes, they have not been entirely satisfactory in all respects.